1. Field of the Invention
This application discloses a combination leaf spring arrangement to close adjacent intake and exhaust valves of an internal combustion engine. Specifically, the leaf spring has an base or edge which is attached to the engine's cylinder head and an unsupported portion extending therefrom in a cantilevered manner. The unsupported portion is separated into two arm portions, one arm engaging an intake valve and the other arm engaging the exhaust valve. The natural resiliency of the cantilevered arms tend to bias the valves towards closed operative positions.
2. Description of the Related Art
The use of springs to close the typical poppet type engine valve is universal at least for passenger vehicle and light truck engines. The coil spring has found wide spread an long term use for this purpose. A disadvantage of coil springs is their relatively great length which results in a larger (higher) cylinder head than would otherwise be desired.
In the 1950's, "mouse trap" type springs were used by Ferrari to reduce cylinder head size. A mouse trap spring is a wire device with a coil formed at a midportion and with its end portions extending therefrom. One of the ends engaged the cylinder head and the other engaged the valve. Opening movement of the valve caused the coil shaped midportion to be rotated which generated a torsion force to yieldably resist opening of the valve. "Mouse trap" type springs are disclosed in U.S. Pat. Nos.: 3,097,633 to Klein; 3,482,555 to Sherbinsky et al; and 4,420,141 to Goloff.
Currently, some racing type engines have replaced the metal valve spring entirely and substituted a variable chamber filled with a compressible gas such as nitrogen.
Also, there are patents disclosing the use of a leaf spring in internal combustion engines. For example, in FIG. 4 of the U.S. Pat. No. 1,236,643 to Adams et al. a leaf spring is disclosed. The specification describes the leaf spring as being supported at a midpoint with the opposite ends engaging inlet valve j and outlet valve l respectively.
In U.S. Pat. No. 1,277,742 to Mummert, a leaf type spring 27 is mounted at a midpoint by shaft 25 with end portions engaging valves 6 and 7. likewise, in U.S. Pat. No. 1,523,583 to Chilton, a multi-layered or laminated leaf spring 29 is mounted at a midpoint with ends engaging valve ends 25 of valves 22, 23.
In U.S. Pat. No. 4,617,882 to Matsomoto discloses a dual overhead camshaft-type cylinder head in which the intake and exhaust cam shafts are gear driven each by a single idler gear which itself is driven by another idler gear which, in turn, is driven by a gear on the engine crankshaft. A disadvantage of this arrangement is the stacked juxtaposition of all these gears which necessitate a fixed geometry of the driving mechanism as well as the spacing of the intake from the exhaust camshaft.
The U.S. Pat. No. 3,602,205 to Turkish discloses a leaf type spring arrangement for a valve requiring a pair of elongated spring members each with one end clamped to the cylinder head and a free end engaging a valve retainer.